Former Trump campaign adviser Richard Gates is reportedly close to a plea deal with special counsel Robert Mueller.

Sources familiar with the case told CNN that Gates has been in negotiations for a plea deal for nearly a month. A plea deal with Mueller could indicate Gates is cooperating with the special counsel’s investigation.

CNN reports that Gates has had a “Queen for a Day” interview with Mueller’s team, a term criminal lawyers use to describe an interview in which a defendant answers questions from prosecutors and can admit to crimes with few consequences.

Meanwhile, Mueller’s investigators are planning to file new charges against Gates that are tax related, sources familiar with the investigation told the network. The additional charges could be used to pressure Gates into cooperating with Mueller’s team.

Additional charges against former Trump campaign chairman Paul Manafort are also being prepared, according to CNN, which reported that Gates's plea deal could be announced within the next week.

Gates hired a top white-collar attorney last month that was spotted meeting twice with Mueller’s team.

The former business associate of Manafort pleaded not guilty in October to eight charges in the probe, including money laundering. Manafort also pleaded not guilty to charges in the same case.

Mueller has filed charges against four figures tied to President Trump in his probe, including Gates and Manafort, whose charges stem from work they did for a pro-Russia political party in Ukraine.

Former national security adviser Michael Flynn and former Trump campaign adviser George Papadopoulos have both pleaded guilty to charges from Mueller. Both Flynn and Papadopoulos have agreed to cooperate with Mueller in the investigation.